Mesa (master): nir/glsl: Emit memory barriers as part of barrier()

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Module: Mesa
Branch: master
Commit: ba43b66dc996988ec326d35395e9699ea4f66fdf
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ba43b66dc996988ec326d35395e9699ea4f66fdf

Author: Jason Ekstrand <jason at jlekstrand.net>
Date:   Tue Jan  7 14:40:53 2020 -0600

nir/glsl: Emit memory barriers as part of barrier()

The GLSL barrier() intrinsic does an implicit shared memory barrier in
compute shaders and an implicit TCS patch output barrier in tessellation
control shaders.  We'd like NIR's barrier intrinsic to just be a control
flow barrier and not have memory implications.  To satisfy this, we need
to add an extra memory barrier in front of each nir_intrinsic_barrier.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>
Reviewed-by: Eric Anholt <eric at anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3307>

---

 src/compiler/glsl/glsl_to_nir.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/compiler/glsl/glsl_to_nir.cpp b/src/compiler/glsl/glsl_to_nir.cpp
index 479832b5ab0..4ab620142b0 100644
--- a/src/compiler/glsl/glsl_to_nir.cpp
+++ b/src/compiler/glsl/glsl_to_nir.cpp
@@ -2701,6 +2701,18 @@ nir_visitor::visit(ir_dereference_array *ir)
 void
 nir_visitor::visit(ir_barrier *)
 {
+   if (shader->info.stage == MESA_SHADER_COMPUTE) {
+      nir_intrinsic_instr *shared_barrier =
+         nir_intrinsic_instr_create(this->shader,
+                                    nir_intrinsic_memory_barrier_shared);
+      nir_builder_instr_insert(&b, &shared_barrier->instr);
+   } else if (shader->info.stage == MESA_SHADER_TESS_CTRL) {
+      nir_intrinsic_instr *patch_barrier =
+         nir_intrinsic_instr_create(this->shader,
+                                    nir_intrinsic_memory_barrier_tcs_patch);
+      nir_builder_instr_insert(&b, &patch_barrier->instr);
+   }
+
    nir_intrinsic_instr *instr =
       nir_intrinsic_instr_create(this->shader, nir_intrinsic_barrier);
    nir_builder_instr_insert(&b, &instr->instr);